powerpc/mm: factor out creating/removing linear mapping

We want to stop abusing memory hotplug infrastructure in memtrace code
to perform allocations and remove the linear mapping. Instead we will use
alloc_contig_pages() and remove the linear mapping manually.

Let's factor out creating/removing the linear mapping into
arch_create_linear_mapping() / arch_remove_linear_mapping() - so in the
future, we might be able to have whole arch_add_memory() /
arch_remove_memory() be implemented in common code.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201111145322.15793-4-david@redhat.com

arch/powerpc/mm/mem.c

@@ -120,34 +120,26 @@ static void flush_dcache_range_chunked(unsigned long start, unsigned long stop,
 	}
 }
 
-int __ref arch_add_memory(int nid, u64 start, u64 size,
-			  struct mhp_params *params)
+int __ref arch_create_linear_mapping(int nid, u64 start, u64 size,
+				     struct mhp_params *params)
 {
-	unsigned long start_pfn = start >> PAGE_SHIFT;
-	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int rc;
 
 	start = (unsigned long)__va(start);
 	rc = create_section_mapping(start, start + size, nid,
 				    params->pgprot);
 	if (rc) {
-		pr_warn("Unable to create mapping for hot added memory 0x%llx..0x%llx: %d\n",
+		pr_warn("Unable to create linear mapping for 0x%llx..0x%llx: %d\n",
 			start, start + size, rc);
 		return -EFAULT;
 	}
-
-	return __add_pages(nid, start_pfn, nr_pages, params);
+	return 0;
 }
 
-void __ref arch_remove_memory(int nid, u64 start, u64 size,
-			     struct vmem_altmap *altmap)
+void __ref arch_remove_linear_mapping(u64 start, u64 size)
 {
-	unsigned long start_pfn = start >> PAGE_SHIFT;
-	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int ret;
 
-	__remove_pages(start_pfn, nr_pages, altmap);
-
 	/* Remove htab bolted mappings for this section of memory */
 	start = (unsigned long)__va(start);
 	flush_dcache_range_chunked(start, start + size, FLUSH_CHUNK_SIZE);
@@ -160,6 +152,29 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size,
 	 */
 	vm_unmap_aliases();
 }
+
+int __ref arch_add_memory(int nid, u64 start, u64 size,
+			  struct mhp_params *params)
+{
+	unsigned long start_pfn = start >> PAGE_SHIFT;
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+	int rc;
+
+	rc = arch_create_linear_mapping(nid, start, size, params);
+	if (rc)
+		return rc;
+	return __add_pages(nid, start_pfn, nr_pages, params);
+}
+
+void __ref arch_remove_memory(int nid, u64 start, u64 size,
+			      struct vmem_altmap *altmap)
+{
+	unsigned long start_pfn = start >> PAGE_SHIFT;
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+
+	__remove_pages(start_pfn, nr_pages, altmap);
+	arch_remove_linear_mapping(start, size);
+}
 #endif
 
 #ifndef CONFIG_NEED_MULTIPLE_NODES

include/linux/memory_hotplug.h

@@ -375,6 +375,9 @@ extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
 					  unsigned long pnum);
 extern struct zone *zone_for_pfn_range(int online_type, int nid, unsigned start_pfn,
 		unsigned long nr_pages);
+extern int arch_create_linear_mapping(int nid, u64 start, u64 size,
+				      struct mhp_params *params);
+void arch_remove_linear_mapping(u64 start, u64 size);
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
 #endif /* __LINUX_MEMORY_HOTPLUG_H */